Route profile
SEA→SLC
Flight reliability, delays and best times to fly from Seattle to Salt Lake City. · 689 miles
Right now
Current conditions at both ends of this route.
Aviation weather is not currently a factor. FAA operational data — ground stops, ground delay programs and closures — is not currently available to FlyerIntel.
Weather conditions are associated with a higher chance of delays. FAA operational data — ground stops, ground delay programs and closures — is not currently available to FlyerIntel.
Airport conditions describe the airfield, not any individual flight. An airport operating normally is not a guarantee that a specific flight will depart on time.
Route reliability
July 2023 – June 2026
Better than 90% of comparable major US routes (4,577 compared)
Calculated from 11,934 flights. How this is calculated
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – June 2026
Best time to fly
On-time arrival rate by scheduled local departure time.
SEA → SLC flights departing 5–9 AM arrived on time 92.5% of the time, against 76.8% for 3–6 PM departures — a gap of 15.7 percentage points.
By departure window
By departure hour
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Buckets with fewer than 120 flights are not scored.
Airlines on this route
Performance by the carrier that actually operated the flight.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| Delta Air Lines | 6,613 | 87.9% | 0.38% | -9 min | 3.3% |
| Alaska Airlines | 3,720 | 78.7% | 1.34% | -3 min | 4.2% |
| SkyWest Airlines | 1,410 | 78.2% | 0.07% | -2 min | 5.1% |
Delta Air Lines arrived on time 9.7 percentage points more often than SkyWest Airlines on this route.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Carriers with fewer than 200 flights on this route are not listed.
Individual flights on this route
The same route is not equally reliable at every hour. These are the flight numbers with enough operating history to judge separately.
| Flight | Scheduled | Operations | On time |
|---|---|---|---|
| DL1128 Delta Air Lines | 5:30 AM | 818 | 92.9% |
| DL1120 Delta Air Lines | 1:30 PM | 754 | 85.4% |
| DL1016 Delta Air Lines | 9:30 AM | 726 | 90.8% |
| DL1165 Delta Air Lines | 5:10 PM | 690 | 80.8% |
| DL1239 Delta Air Lines | 7:30 PM | 561 | 83.0% |
| DL1265 Delta Air Lines | 11:15 AM | 484 | 87.3% |
| OO3298 SkyWest Airlines | 7:16 PM | 375 | 79.5% |
| AS430 Alaska Airlines | 7:05 AM | 294 | 93.1% |
| AS733 Alaska Airlines | 11:38 AM | 290 | 66.0% |
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Flight numbers with fewer than 270 operations on this route, or no longer scheduled, are not listed.
Weekly and seasonal patterns
By day of week
Wednesday is historically the most reliable day and Sunday the least, a gap of 4.7 percentage points.
By month
July is historically the weakest month and April the strongest, a spread of 10.4 percentage points.
Historical trend
On-time arrival rate by month.
Over the most recent 12 months (2025-07 to 2026-06), on-time arrivals averaged 83.6% against 83.7% in the 12 months before — broadly unchanged.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026
Data and methodology
All figures on this page are calculated by FlyerIntel from 11,934 SEA → SLC flight records published by the US DOT Bureau of Transportation Statistics, covering July 2023 – June 2026. A flight is counted as delayed when it arrives 15 or more minutes after its scheduled arrival time, following BTS methodology. Cancelled and diverted flights have no arrival time and are excluded from on-time rates rather than counted as late.